A State-of-the-Art Review on Sustainable Chemical Stabilizers for Expansive Soils

Expansive soils are susceptible to significant volumetric changes due to the fluctuating moisture levels caused by the infiltration and evaporation of water. This has often resulted in destructive consequences for the structures they support. Various stabilization methods were developed and adopted to enhance their properties and make them suitable for construction purposes. Traditional stabilizers have an adverse impact on the ecosystem by releasing harmful greenhouse gases in the atmosphere and leaching of toxic chemical compounds into the groundwater. Hence, in the past few decades, research on soil stabilization has mainly focused on the utilization of various chemical additives that are environmentally friendly and durable for a longer period of time. This paper is aimed at providing a state-of-the-art review of some of the recent, emerging, and sustainable chemical additives for improving the engineering properties of expansive soil. The efficiency of various additives categorized under industrial by-products, synthetic polymers, biopolymers, geopolymers, and enzymes is discussed here. First, the interaction mechanism between different chemical additives and soil particles during the stabilization process is reviewed. Then, the effect of these additives on some of the crucial geotechnical parameters of expansive soils is discussed in detail. Emphasis is placed on the plasticity characteristics, swell-shrink behaviour, unconfined compressive strength, and compaction properties of expansive soils. The paper also comments on the challenges involved in the utilization of these additives for practical applications. Laboratory test results for various stabilized soils are interpreted by understanding the stabilization mechanism for their successful field application in the future.